Thermally reversible fluorans: Synthesis, thermochromic properties and real time application

Article abstract of DOI:10.1166/jnn.2018.14705

In the present study, two fluoran molecules (TH1 and TH2) have been synthesized, and their reversible thermochromic properties have been investigated. This work demonstrates the thermochromic reversibility of the fluoran. Furthermore, the three-component mixtures that comprising fluorans (TH1/TH2), bisphenol-A (color developer), and methyl stearate a low melting solvent were used to examine the thermochromic behavior with sturdy heating and cooling rates and the thermochromic properties of the fluorans were detailed using UV-Vis, reflectance and FT-IR spectroscopic techniques. Finally, test strip similar to pH paper and acrylic fiber a versatile material used as thermal indicators also been successfully made from these two fluoran derivatives.

Full text of DOI:10.1166/jnn.2018.14705

Article
Journal of
Nanoscience and Nanotechnology
Vol. 18, 3299–3305, 2018
Copyright © 2018 American Scientific Publishers
All rights reserved
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Printed in the United States of America
Thermally Reversible Fluorans: Synthesis,
Thermochromic Properties and Real Time Application
Ick Jin Kim†, Ramalingam Manivannan†, and Young-A Son∗
Department of Advanced Organic Materials Engineering, Chungnam National University, 220 Gung-Dong,
Yuseong-gu, Daejeon 305-764, South Korea
In the present study, two fluoran molecules (TH1 and TH2) have been synthesized, and their
reversible thermochromic properties have been investigated. This work demonstrates the ther-
mochromic reversibility of the fluoran. Furthermore, the three-component mixtures that comprising
fluorans (TH1/TH2), bisphenol-A (color developer), and methyl stearate a low melting solvent were
used to examine the thermochromic behavior with sturdy heating and cooling rates and the ther-
mochromic properties of the fluorans were detailed using UV-Vis, reflectance and FT-IR spectro-
scopic techniques. Finally, test strip similar to pH paper and acrylic fiber a versatile material used
as thermal indicators also been successfully made from these two fluoran derivatives.
Keywords: Fluorans, Thermochromic, Reversible, Thermal Indicator, Acrylic Fiber.
IP: 94.45.153.233 On: Thu, 14 Jun 2018 07:01:50
Copyright: American Scientific Publishers
1. INTRODUCTION
controlled proportional ratios, the color formers and devel-
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opers are dissolved in the low melting co-solvent and then
the solution changes its color when it is cooled. Thus,
the stimulation of the thermochromic effects is mainly
dependent on the design of a system with warming and
cooling. These types of functional dyes in the solid state
undergo a ring-opening reaction and giving rise to a strik-
ing color change when it in comes in contact with acid and
these changes are reversible with the change in tempera-
ture (Scheme 1).24–26 Since these systems involve changes
in the phase between colored solid and colorless liquid
phase, then the thermochromic properties do not affected
much when the ratio of the components maintained for
microencapsulation.27
Fluorans have wide spread utility as it is used as copying
material, in pressure and temperature-sensitive recording
materials.28–30 In general, fluoran dyes are usually designed
in such a way that contains a N ,N -dialkylamino group
at the meta position of the xanthene ring. Shen Meiqin
and coworkers8 listed the thermochromic properties of flu-
oran red and black dyes like the above mentioned frame
work. Hojo et al. have developed fluoran moiety and inves-
tigated the reversible properties of corresponding fluorans
with acid developers together with Mg2+ and macrocyclic
polyamine.31 Intrinsic thermochromic properties, the flu-
oran itself possess thermochromic characteristics or ther-
mochromic packings added into the polymer matrix.32ꢀ33
Bis fluoran derivatives has also been reported where the
Development of thermochromic materials has attracted
much attention in recent years due its significant changes
in their optical properties in response to external stim-
ulation, giving them several prospective applications
such as sensors, thermal indicators, memory storage
devices, security inks, dyes for solar cell application and
other luminescent switches.1–7 Many leuco dyes (fluorans
and crystal violet lactone), spiropyrans, inorganic com-
plexes and conjugated polymers,8–14 have been researched.
The (thio)xanthene unit15 forms the core of many
functional dyes including rhodamines,16 rosamines,17
thiofluoresceins18 and fluorans19 were known to act as ther-
mochromic materials. Among these, fluorans have been
explored with a greater extent on their commercial appli-
cations in recent years. In addition, the dyes, which have
been derived from a xanthene core, displays electrochromic
property when applied an appropriate potential.20ꢀ21
A large number of fluoran {spiro furan, xanthene-
3-one} compounds can act as thermochromic materi-
als through thermochromic formulations incorporate three
component systems, includes a fluoran (color former) and
a Bronsted acid (color developer) in a low melting sol-
vent, such as methyl stearate.19ꢀ22ꢀ23 When the three com-
ponent mixtures outlined above are heated together in the
∗Author to whom correspondence should be addressed.
†These two authors contributed equally to this work.
J. Nanosci. Nanotechnol. 2018, Vol. 18, No. 5
1533-4880/2018/18/3299/007
doi:10.1166/jnn.2018.14705
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Thermally Reversible Fluorans: Synthesis, Thermochromic Properties and Real Time Application
Kim et al.
with a diamond probe ATR attachment (neat sample). ESI-
mass spectra were recorded using a Thermo Scientific LTQ
Orbitrap XL Fourier transform mass spectrometer. The key
intermediates and fluorans (TH1 and TH2) for the present
study were prepared according to the literature procedures
(Scheme 2).35 For practical application Whatman grade 42
filter paper were used and dip coating method was adopted
to apply TH1/TH2 in filter paper/Acrylic fiber.
2.2. General Method for the Preparation of
Intermediates (1, 2)
Scheme 1. Thermochromic response of fluorans-bisphenol A system.
A solution of 3-dimethylamino phenol or 3-diethylamino
phenol (1.0 mmol) and phthalic anhydride (1.0 mmol) in
toluene was refluxed under N2 for 5 h and then allowed
thermochromic behavior of those fluoran were not dis-
cussed in detail.34 In this present study, we synthesized
two fluoran moieties with a variation in N ,N -dialkylamino
(methyl/ethyl) group at the meta position of the xanthene
oxygen Likewise, we discuss the thermochromic properties
of the fluorans (TH1 and TH2) with respect to electronic
effects in solid state.
ꢀ
to stir at 60 C for 1 h. Then 35% aqueous NaOH was
slowly added to the reaction mixture at 60 ꢀC and heated at
90 ꢀC for 12 h. The resulting mixture was ꢀpoured into dis-
tilled water, acidified with conc. HCl at 0 C, and allowed
to stir at room temperature for 2 h. The suspension was
then filtered and was then dried to afford a pink solid. The
obtained crude material was then purified by column chro-
matography with gradient enhancement of ethylacetate in
petroleum ether. The products 1 and 2 were characterized
2. EXPERIMENTAL SECTION
2.1. Equipment and Reagents
All reagents were purchased from either Aldrich or TCI
chemicals and were used as received. NMR spectra
were recorded on a Bruker Avance 300 MHz instrument
(1H NMR 300 MHz, 13C NMR 150 MHz) with tetram-
ethylsilane as an internal reference. All new compounds
were homogeneous by TLC performed on either Merck
1
using H NMR, 13C NMR and ESI mass spectral tech-
niques. The results obtained are;
2.2.1. 2-(4-(dimethylamino)-2-hydroxybenzoyl)Benzoic
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Acid (1)
Copyright: American Scientific Publishers
1H NMR (CDCl , 300 MHz), ꢁ (ppm): 2.94 (s, 6H), 5.98
TLC aluminum or silica gel 60 F254 sheets using a range
Delivered by Ingenta
3
(m, 1H), 6.07 (d, 1H, J = 1.8 Hz), 6.8 (d, 1H, J = 6 Hz),
7.26 (d, 1H, J = 7.2 Hz), 7.44 (t, 1H, J = 7.2 Hz), 7.53
(t, 1H, J = 7.2 Hz), 8.0 (d, 1H, J = 7.8 Hz), 12.43 (s, 1H)
(Fig. S1).
of eluent systems with differing polarities. Flash column
chromatography was performed on chromatography silica
gel (230–400 mesh). Solid state UV-Vis and reflectance
spectra of the new thermochromic compounds in methyl
stearate and bisphenol-A were performed on a Shimadzu
Solid Spec-3700. FT-IR spectra were recorded using a
Perkin Elmer Spectrum One spectrophotometer equipped
13C NMR (CDCl3, 150 MHz) ꢁ (ppm): 39.95, 97.76,
104.03, 110.34, 127.78, 127.98, 129.20, 131.06, 132.77,
134.32, 141.18, 155.98, 165.13, 170.23, 198.75 (Fig. S2).
Scheme 2. Synthetic route for preparation of fluorans TH1 and TH2.
3300
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Kim et al.
Thermally Reversible Fluorans: Synthesis, Thermochromic Properties and Real Time Application
ESI-MS (m/z) calcd. 285.1, found 283.8 (M − H+ꢂ
A
B
(Fig. S3).
TH1
TH2
2.2.2. 2-(4-(diethylamino)-2-hydroxybenzoyl)Benzoic
Acid (2)
1H NMR (CDCl3, 300 MHz), ꢁ (ppm): 1.09 (t, 6H, J =
14.1 Hz), 3.275 (m, 4H), 5.95 (dd, 1H, J = 9, 9.3 Hz),
6.07 (d, 1H, J = 2.4 Hz), 6.79 (d, 1H, J = 9.3 Hz), 7.28
(d, 1H, J = 7.5 Hz), 7.44 (t, 1H, J = 14.7 Hz), 7.53 (t, 1H,
J = 14.7 Hz), 8.02 (d, 1H, J = 7.8 Hz), 12.46 (s, 1H)
(Fig. S4).
Figure 1. The color of TH1 and TH2 in (A) acetonitrile and (B) acetic
acid.
13C NMR (CDCl3, 150 MHz) ꢁ (ppm): 11.61, 43.69,
96.13, 102.77, 108.93, 127.15, 128.21, 130.11, 131.59,
133.65, 139.99, 153.05, 164.59, 167.22, 197.20 (Fig. S5).
ESI-MS (m/z) calcd. 313.1, found 313.9 (M + H+ꢂ
(Fig. S6).
J = 7.8 Hz), 7.61 (t, 1H, J = 15 Hz), 7.94 (d, 1H, J =
7.8 Hz) (Fig. S10).
13C NMR (CDCl3, 150 MHz) ꢁ (ppm): 11.46, 43.47,
82.18, 96.51, 103.44, 107.64, 114.21, 117.90, 120.49,
122.97, 124.08, 125.85, 127.78, 128.79, 129.52, 132.30,
134.03, 148.73, 149.81, 151.50, 151.67, 168.29 (Fig. S11).
ESI-MS (m/z) calcd. 449.06, found 450.1 (M + H+ꢂ
(Fig. S12).
2.3. General Method for the Preparation of
TH1 and TH2
A solution of 2-(4-(dimethylamino)-2-hydroxybenzoyl)
benzoic acid (1) or 2-(4-(diethylamino)-2-hydroxy-
benzoyl)benzoic acid (2) (1 mmol) and 4-bromophenol
(1 mmol) in methanesulfonic acid (5 mL) was heated up
to 60–90 ꢀC for 2 h. Then the reaction mixture was cooled
to room temperature and 25% of NaOH (20 mL) solution
was slowly added into the reaction mixture. The resulting
alkaline mixture was stirred at room temperature for 1 h.
The formed solid was filtered through the filter paper and
3. RESULTS AND DISCUSSION
3.1. Color Properties in Different Solvents
With the instantaneous addition of fluorans TH1 and TH2
in aprotic solvents such as toluene, benzene, tetrahydro-
furan, and acetonitrile, no obvious color change has been
observed (Figs. 1(A) and S13). This signifies that in apro-
IP: 94.45.153.233 On: Thu, 14 Jun 2018 07:01:50
tic solvents, these compounds substantially can be found
Copyright: American Scientific Publishers
to be in colorless lactone form. Meanwhile, in an acetic
the obtained crude material was purified by column chro-
matography with gradient enhancement of ethylacetate in
petroleum ether. The products TH1 and TH2 were charac-
Delivered by Ingenta
acid solution, the color of the solution converted to deep
orange red color (Fig. 1(B)) is mainly due to the formation
of zwitterions of the fluoran moiety.
1
terized using H NMR, 13C NMR and ESI mass spectral
techniques. The results obtained are;
3.2. UV-Vis Spectral Studies
2.3.1. 2ꢀ-Bromo-6ꢀ-(dimethylamino)-3H-
To determine the electronic change and to confirm the
mechanism of the fluoran ring, the UV-Vis spectral study
of TH1 and TH2 were recorded in acetonitrile as well as
with the addition of small amount of acetic acid to the
same. The observed peaks at approximately 300–330 nm
in the absorbance spectra of TH1 and TH2 in acetoni-
trile is due to the colorless ring-closed lactone structure
(Fig. 2). In the case of acetic acid medium, these fluorans
showed two new broad peaks in the range of 490–530 nm.
Thus the addition of acetic acid resulting in the formation
of zwitterions of the fluoran moiety makes the n–ꢃ∗ tran-
sition relatively easier giving rise to a striking color change
from colorless to deep orange red to the ring opened flu-
oran system. This result reveals that even in the solution
state the fluoran has a significant role in both neutral and
in acidic medium.
Spiro[isobenzofuran-1,9ꢀ-xanthen]-3-One (TH1)
1H NMR (CDCl3, 600 MHz), (ppm): 2.90 (s, 6H), 6.32
(dd, 1H, J = 8.4, 9 Hz), 6.40 (d, 1H, J = 2.4 Hz), 6.51
(d, 1H, J = 9 Hz), 6.79 (d, 1H, J = 2.4 Hz), 7.06 (m,
2H), 7.36 (dd, 1H, J = 9, 9 Hz), 7.53 (m, 2H), 7.94 (d,
1H, J = 7.8 Hz) (Fig. S7).
13C NMR (CDCl3, 150 MHz) ꢁ (ppm): 39.15, 81.95,
97.38, 104.43, 108.15, 117.94, 120.41, 122.89, 124.11,
125.66, 127.56, 128.83, 129.50, 132.35, 134.09, 149.72,
151.13, 151.21, 151.80, 168.29 (Fig. S8).
ESI-MS (m/z) calcd. 421.03, found 422.1 (M + H+ꢂ
(Fig. S9).
2.3.2. 2ꢁ-Bromo-6ꢁ-(diethylamino)-3H-Spiro
[isobenzofnnuran-1,9ꢁ-xanthen]-3-One (TH2)
1H NMR (CDCl3, 600 MHz), (ppm): 1.08 (t, 6H, J =
7.2 Hz), 3.26 (m, 4H), 6.27 (dd, 1H, J = 9, 9 Hz), 6.36
(d, 1H, J = 2.4 Hz), 6.47 (d, 1H, J = 9 Hz), 6.78 (d,
1H, J = 2.4 Hz), 7.06 (d, 1H, J = 8.4 Hz), 7.1 (d, 1H,
J = 7.8 Hz), 7.36 (dd, 1H, J = 8.4, 8.4 Hz), 7.53 (t, 1H,
3.3. Thermochromic Properties in the Solid State
In general the thermochromic materials form a composite
with three components which includes
(i) fluoron molecules (TH1 and TH2);
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Thermally Reversible Fluorans: Synthesis, Thermochromic Properties and Real Time Application
Kim et al.
Figure 4. Changes of orbital hybridization at fluorans spiro ring with
proton donors.
moiety and the spirolactone unit. However, in reality, the
reason for the color change of TH1 and TH2 is due to
the fact that: TH1 and TH2 are colorless (proton accep-
tors) because the carbon atom at center of a spiro molecule
forms a bond with other carbon atoms through its sp3
hybrid orbitals, forming the colorless lactone ring. When
TH1 and TH2 are in contact with a proton donor (bisphe-
nol A), the lactone ring opens, and the sp3 hybridized
orbital of the central carbon atom gets modified to a sp2
hybrid orbital (Fig. 4). Due to this factor the ꢃ-conjugation
of the fluoran moiety has been extended and the ꢄmax was
moved to higher wavelength.8
Figure 2. (A) UV-vis absorption spectra of (TH1 and TH2) in acetoni-
trile and in acetic acid, (B) ꢄmax of (TH1 and TH2) in acetic acid.
3.4. Solid State Spectroscopic Studies
(ii) acid activator (bisphenol-A) which is capable of
reversibly accepting an electron from the electron-
donating component; and
(iii) a low melting solvent such as methyl stearate has
a capability to control the temperature and sensitivity of
To elucidate the electronic properties of these systems in
detail, we employed solid state UV-Vis spectroscopic anal-
IP: 94.45.153.233 On: Thu, 14 Jun 2018 07:01:50
ysis by varying the temperatures (Fig. 5). As shown in
Copyright: American Scientific Publishers
Delivered bythInegfiegnutrae the fluoran moietyꢀ (TH1 and TH2) showed no
the thermochromic material in its coloration/decoloration
phenomenon.
peaks around 500 nm at 40 C, whereas, when cooled to
RT, these thermochromic materials exhibited two absorp-
tion peaks at approximately 500 to 550 nm. This is nor-
mally due to the ring-opening of the fluoran through the
intermolecular effect between the electron acceptor pheno-
lic and the spirolactone unit.24–26ꢀ36
In general these thermochromic mixtures (TH1 and TH2)
are deep orange red color when it is cooled, but they
become decolorized while warmed (Fig. 3). In the methyl
stearate system, both fluorans (TH1 and TH2) demon-
The changes in the reflectance of the fluorans (TH1 and
TH2) in methyl stearate and bisphenol A at different tem-
peratures are shown by the reflectance spectra (Fig. ꢀ6).
The spectra showed peaks around 450–600 nm at 24 C,
mainly because of the ring opened form of the fluorans
(TH1 and TH2). Whereas, when the temperature is raised
ꢀ
strated color reversibility at 40 C. The ongoing studies
indicated that the colorless semisolid (TH1 and TH2) sys-
tems turned to a deep orange red color as a result of the
ring-opening fluoran system, likely due to the intermolec-
ular association between the electron acceptor phenolic
ꢀ
up to 40 C, the color of the mixture was disappeared due
to the regeneration of the lactone ring. The role of color
developer has been cross verified by carrying out the same
experiment in the absence of bisphenol-A, the added TH1
(5 mg) and methyl stearate (10 mg) without bisphenol-A
showed no distinct color change upon heating up to 40 ꢀC
due to the lack of proton donor in the combined mixture.
3.5. FT-IR Spectroscopic Studies
FT-IR spectral studies was carried out to confirm the struc-
ture of the fluoran molecule, for the above-mentioned ther-
mochromic material (TH1 and TH2) has been recorded
ꢀ
ꢀ
at different temperatures (24 C and 40 C) (Fig. 7). The
Figure 3. Solid state color change of fluorans TH1 and TH2 with
bisphenol-A and methylsterate.
results from the FT-IR spectra indicated that the shifts in
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Kim et al.
Thermally Reversible Fluorans: Synthesis, Thermochromic Properties and Real Time Application
Figure 5. Solid state UV-vis spectra of TH1 and TH2 at 24 ꢀC (cool) and 40 ꢀC (heating).
positions of peaks could be endorsed due to the modi-
fication in the electronic structure of the thermochromic
systems. For both TH1 and TH2 system, the peak at the
range of 1754 and 1750 cm−1 in the colorless sample
(at 40 ꢀC) has been shifted to 1738 cm−1 in the orange red
colored sample. The value of 1750 cm−1 is corresponds to
the C O stretching frequency.37ꢀ38 This result reveals that
the decrease in the frequency of the C O group in the
form TH1+ are shown in Figure 8. The relevant frontier
orbitals and its energy gap (ꢅE = EHOMO–ELUMOꢂ for TH1
and TH1+ are depicted in Figure 9. In TH1, the HOMO is
confined on the xanthene unit and the LUMO on the lac-
tone unit while in the case of ring opened form (TH1+),
the LUMO is uniformly distributed throughout the entire
molecule when compared to that of the HOMO. This is
due to the fact that the ring opened form possesses a larger
cooling state is mainly because of the ester ring opening,
electronic cloud than the lactone form. The above results
indicated that the ꢅE value of TH1 is relatively lesser
when compared to that of the TH1. This is in good agree-
ment with the results observed in the electronic spectra of
the fluoran moiety.
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+
Copyright: American Scientific Publishers
resulting in the formation of a carboxylate group which
can be easily protonated.37
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3.6. Theoretical Study
To gain further understanding in the mechanism of fluo-
ran moiety TH1, molecular modeling was performed using
Density Functional Theory calculations at B3LYP/321G
level of theory using Gaussian 03 package.39 In the opti-
mized geometry of the lactone TH1 and the ring opened
3.7. Application as Thermal Indicator
Motivated by the favorable fluoran color former TH1 and
TH2 in which the devising contains TH1 or TH2 in low
melting solvent methyl stearate containing bisphenol A,
Figure 6. Solid state reflactance spectra of TH1 and TH2 at 24 ꢀC (cool) and 40 ꢀC (heating).
J. Nanosci. Nanotechnol. 18, 3299–3305, 2018
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Thermally Reversible Fluorans: Synthesis, Thermochromic Properties and Real Time Application
Kim et al.
Figure 7. FT-IR spectra of TH1 and TH2 at heat (40 ꢀC) and cool (24 ꢀC).
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+
Figure 8.
Optimized geometry of TH1 and TCHo1 p.yright: American Scientific Publishers
Delivered by Ingenta
and monitored change in the color of the mixture on test
strip and in acrylic fiber (as a thermal indicator). In this
work, a color former combination of thermal indicator
comprising TH1 or TH2 (5 wt.%), bisphenol A (2.5 wt.%)
and methyl stearate (92.5 wt.%) was prepared. The TH1
or TH2 and bisphenol-A, which gets dissolved in methyl
stearate at about 90 C. The filter paper/acrylic fiber was
ꢀ
dipped into the solution which is colorless and then cooled.
During this process, TH1/TH2 developed an orange red
color as a result of ring-opening of the lactone ring through
intermolecular association of the phenolic moieties with
the spirolactone units (Figs. 10 and S14). The acrylic fiber
has also been observed to act as an extreme thermal indi-
cator. As depicted in Figures 10 and S14. Depending on
the temperature, the color of the material changed from
orange red to colorless and vice-versa.
Figure 10. (A) Color change of TH1 coated thermal indicator paper at
20 ꢀC and 40 ꢀC, (B) color change of TH1 coated acrylic fiber at 20 ꢀC
and 40 ꢀC.
Figure 9. HOMO–LUMO orbitals of the TH1 and TH1+ and their
energy level diagram.
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Kim et al.
Thermally Reversible Fluorans: Synthesis, Thermochromic Properties and Real Time Application
4. CONCLUSION
20. W. Weng, T. Higuchi, M. Suzuki, T. Fukuoka, T. Shimomura,
M. Ono, L. Radhakrishnan, H. Wang, N. Suzuki, H. Oveisi, and
We have designed and synthesized two new fluoran moiety
in which the lactone unit acts as a basic skeleton to pro-
duce promising compound for new leuco dyes. The role of
the fluoran moiety possessing lactone ring has been effec-
tively verified under acidic conditions. The color change
of TH1/TH2, bisphenol-A in methyl stearate (colorless to
orange red color) has been tested on both test paper and
acrylic fiber, which can act as a potential thermal indicator
in real time application.
Y. Yamauchi, Angew. Chem. Int. Ed. 49, 3956 (2010).
21. K. Kanazawa, K. Nakamura, and N. Kobayashi J. Phys. Chem. A
118, 6026 (2014).
22. S. Yamamoto, H. Furuya, K. Tsutsui, S. Ueno, and K. Sato, Cryst.
Growth Des. 8, 2256 (2008).
23. D. C. Maclaren and M. A. White, J. Mater. Chem. 13, 1701 (2003).
24. S. M. Burkinshaw, J. Griffiths, and A. D. Towns J. Mater. Chem.
8, 2677 (1998).
25. Y. Sekiguchi, S. Takayama, T. Gotanda, and K. Sano, Chem. Lett.
36, 1010 (2007).
26. D. C. Maclaren and M. A. White, J. Mater. Chem. 13, 1695 (2003).
27. G. P. Ritesh, P. P. Manish, and G. P. Ranjan, Dyes Pigm. 66, 7
(2005).
28. R. Zink, United States Patent No. 4,770,904 (1998).
29. R. Garner and J. C. Petitpierre, United States Patent No. 4,349,218
(1982).
Acknowledgments: This study was supported by the
National Research Foundation of Korea (NRF) funded by
the Ministry of Science, ICT and Future Planning (Grant
no. NRF-2014M3C1A9060739).
30. R. Garner and J. C. Petitpierre, United States Patent No. 3,929,831
(1975).
31. M. Hojo, T. Ueda, A. Inoue, and S. Tokita J. Mol. Liq. 148, 109
(2009).
32. F. Azizian, A. J. Field, B. M. Heron, and C. Kilner, Chem. Commun.
48, 750 (2012).
33. F. Azizian, A. J. Field, J. Griffiths, and B. M. Heron Dyes Pigm.
92, 524 (2011).
34. G. P. Ritesh, V. P. Jignesh, P. P. Manish, and G. P. Ranjan J. Serb.
Chem. Soc. 68, 607 (2003).
35. Q. H. Liu, X. L. Yan, J. C. Guo, D. H. Wang, L. Li, F. Y. Yan, and
L. G. Chen, Spectrochim. Acta A 73, 789 (2009).
36. Y. Takahashi, A. Shirai, T. Segawa, T. Takahashi, and K. Sakakibara,
Bull. Chem. Soc. Jpn. 75, 2225 (2002).
References and Notes
1. X. L. Luo, J. N. Li, C. H. Li, L. P. Heng, Y. Q. Dong, Z. P. Liu,
Z. Bo, and B. Z. Tang, Adv. Mater. 23, 3261 (2011).
2. S. H. Kim, I. J. Hwang, S. Y. Gwon, and Y. A. Son, Dyes Pigm.
87, 158 (2010).
3. Y. L. Chen, A. J. H. Spiering, S. Karthikeyan, G. W. M. Peters,
E. W. Meijer, and R. P. Sijbesma Nat. Chem. 4, 559 (2012).
4. A. Pucci, F. Di Cuia, F. Signori, and G. Ruggeri, J. Mater. Chem.
17, 783 (2007).
5. Y. Q. Dong, J. W. Y. Lam, A. J. Qin, J. Z. Liu, Z. Li, and B. Z.
Tang, Appl. Phys. Lett. 91, 011111 (2007).
6. A. Kishimura, T. Yamashita, K. Yamaguchi, and T. Aida, Nat. Mater.
4, 546 (2005).
7. A. Hagfeldt, G. Boschloo, L. Sun, L. Kloo, and H. Pettersson Chem.
37. K. Costello, K. T. Doan, K. L. Organtini, J. Wilson, M. Boyer,
IP: 94.45.153.233 On: Thu, 14 Jun 2018 07:01:50
G. Gibbs, and L. J. Tribe, Chem. Educ. 91, 883 (2014).
Copyright: American S3c8i.enRt.ifMic. PSuilvbelrisstehine,rsG. C. Bassler, and T. C. Morrill, Spectromet-
Rev. 110, 6595 (2010).
Delivered by Ingenta
ric Identification of Organic Compounds, 5th edn., Weinheim, John
Wiley and Sons, Germany (1991).
8. S. Meiqin, S. Yun, and T. Qiyu, Dyes Pigm. 29, 45 (1995).
9. C. F. Zhu and A. B. Wu, Thermochim. Acta 425, 7 (2005).
10. N. Carmona, V. Bouzas, F. Jimenez, M. Plaza, L. Perez, M. A.
Garcia, M. A. Villegas, and J. Llopis, Sens. Actuators B 145, 139
(2010).
11. X. Chen and J. A. Yoon, Dyes Pigm. 89, 194 (2011).
12. L. Ying, F. Huang, and G. C. Bazan, Nat. Commun. 8, 14047 (2017).
13. S. Sugano and H. Kouzai, Bull. Chem. Soc. Jpn. 89, 27 (2016).
14. J. Xie, C. E. Zhao, Z. Q. Lin, P. Y. Gu, and Q. Zhang, Chem. Asian
J. 11, 1489 (2016).
15. P. Wight, Kirk-Othmer Encyclopaedia of Chemical Technology,
New York, Wiley (2000).
16. K. Kolmakov, V. N. Belov, J. Bierwagen, C. Ringemann, V. Müller,
and C. Eggeling, Chem. Eur. J. 16, 158 (2010).
17. L. Wu and K. Burgess, J. Org. Chem. 73, 8711 (2008).
18. K. Dahms, A. S. Batsanov, and M. R. Bryce, Tetrahedron Lett.
51, 6605 (2010).
19. M. Inouye, K. Tsuchiya, and T. Kitao, Angew. Chem. Int. Ed. 31, 204
(1992).
39. M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A.
Robb, J. R. Cheeseman, J. A. Jr., Montgomery, T. Vreven, K. N.
Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi,
V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda,
J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken,
C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala,
K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G.
Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas,
D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman,
J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski,
B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi,
R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng,
A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson,
W. Chen, M. W. Wong, C. Gonzalez, and J. A. Pople, Gaussian, 03,
Revision D.01, Gaussian, Inc., Wallingford, CT (2004).
Received: 1 April 2017. Accepted: 29 April 2017.
J. Nanosci. Nanotechnol. 18, 3299–3305, 2018
3305